(a) FIeld of the Invention
This invention relates to an apparatus for measuring physical properties of molten polymers and resins. More specifically, this invention is directed to a rheometer for measuring the physical properties of polymers and resins in the molten state.
(b) The Prior Art
Over the years in addition to the melt indexer there have been a number of rheometers for the examination of polymer melts, plate and plate, cone and plate, cone and cone, etc. Other than the melt indexer all these were cumbersome, difficult to operate, poor in reproducibility, time consuming and, in most cases, the data obtained was difficult to interpret.
In this invention the data is readily obtained and a wide range of shear rates may be determined in a minimum of time, each determination covering but a few seconds. The determinations are made in a homogenous shear field with neglible end effects.
Both the shear stress and the normal stress are measured simultaneously in the same shear field. Due to the slit die design of this invention, the polymer properties can be obtained at negligible thermal gradient with rapidity of determination. In addition, thin polymer films are obtained by stripping from the steel tape which provides additional data about the polymer or resin.
In previously developed rheometers a number were difficult to operate; some requiring special training, and most required considerable time per determination and disassembly and cleaning between determinations.
It is the object of this invention to provide a rheometer which is capable of easy operation and which provides rapidity of individual determinations.
It is a further object of this invention to provide a rheometer which may be operated for long periods of time without cleaning or disassembly. In addition, it is the object of this invention to provide a useful end product of each determination, namely a thin polymer film which may be critically examined either photographically or optically, and thereby provide additional information about the polymer.